Novel fabric of improved cover and reduced slickness



July 9, 1963 H. MESSINGER 3,096,563

NOVEL FABRIC OF IMPROVED COVER AND REDUCED sucxmzss Filed June 18, 1959 WITH WATER AT WET FABRIC HEATED UNDER PRESSURE PRESSURE RELEASED WATER IMMEDIATELY VAPOR IZ ES INVENTOR LESTER HUBER MESSING FABRIC WET United States Patent '0, ce

3,096,563 NOVEL FABRIC F IMPROVED COVER AND REDUCED SLICKNESS Lester Hubert Messinger, Newark, Del., assignor to E. I. du Pont de. Nemours. and Company, Wilmington, Del., a corporation of Delaware Filed June 18, 1959, Ser. No. 821,127 11 Claims. (Cl. 28-78) This invention relates to a novel and useful product and to a process for producing the product. More particularly, it relates to a fabric having improved cover and reduced slickness and a process for forming the fabric in an inexpensive manner.

Fabrics woven and knitted from continuous filament yarns of the synthetic fiber group are deficient in fabric aesthetics in that they possess a smooth sheen, do not cover well, and the smooth, close contact with the skin makes them feel hot and clammy in summer and cold in winter. These fabrics possess properties which are distinctly different from fabrics made of spun yarns from synthetic staple fibers, which possess loose ends on the short fibers and reduce the effect of the three above-mentioned objections when used in wearing apparel. However, even fabrics of spun synthetic yarns are not entirely comfortable and need improvement.

It is an object of this invention to provide a fabric having improved aesthetics. Another object is to provide a process for improving the aesthetics of woven knitted or nonwoven fabrics containing continuous filament yarns or staple yarns of synthetic high-melting, fiber-forming polymers. A still further object is to remove the sheen from said fabrics, increase the fabric cover and reduce the fabric slickness by providing a multiplicity of extended protrusions on the surface of the individual filaments so that they project outwardly from the fabric surface. Other objects will become apparent as the description of the invention proceeds.

These objects are accomplished by the present invention which provides an improved fabric containing a preponderance of filaments composed of a synthetic, fiberforming polymer having a melting point above about 250 F. at least some of which filaments are on the fabric surface and contain a multiplicity of extended protrusions which project outwardly from the fabric surface, most of the said extended protrusions of each individual filament having a length greater than the width of the individual filament and being smaller in cross section than the individual filament at the mid-point of the length of the protrusion.

The present invention also provides a process for improving the aesthetics of a fabric containing a preponderance of filaments composed of a synthetic, fiber-forming polymer having a melting point above about 250 F.

- which comprises confining the fabric, which is wet with water at a temperature of 175 F. to 225 F., between confining structures, heating the fabric and water to a temperature of from 100 to 'F. below the softening point of the said synthetic polymer while maintaining sufficient pressure between the confining structures to maintain the fabric in the wet condition and thereafter immediately releasing the pressure from the fabric.

The term preponderance is used to signify that the fabric is composed of more than 50% (on a weight basis) of filaments (either staple or continuous filaments) formed from the synthetic polymer. By synthetic, fiber-forming polymer is meant a manmade, non-cellulosic polymer which is suitable for the formation of textile fibers. Many such suitable materials are included with the descriptions of United States Patent Nos. 2,190,770, 2,130,948, 2,667,468, 2,465,319, and 2,511,544.

, The terminology extended protrusions which project out- 3,096,563 Patented July 9, 1963 filament from which they project and in addition are smaller than the filament in cross section at the midpoint of the length of the protrusion. With circular filaments and the somewhat circular hair-like extended protrusions, it has been found that the average diameter of the protrusion is generally somewhat less than /5 the average diameter of the filament from which it originates and the length of the protrusion is generally two or more times the filament diameter. The term confining structures is used to mean structures which hold and confine the fabric (as well as the water in the fabric) under sufficient pressure that the water is held within the fabric until the release of the pressure. Thus, even though the water is heated to a temperature above its boiling point,

it is still confined within the fabric until the pressure is released. Upon the release of pressure, however, the water immediately vaporizes and leaves the fabric in the form of steam.

In a preferred embodiment of the present invention, a fabric which is composed of continuous filaments of poly(hexamethylene adiparnide) or poly(ethylene terephthalate), is wet with water, and is passed at a speed of from about 15 to about 35 yards per minute between the two confining rollers of a conventional calender machine to exert a pressure on the fabric of from about 500 to about 2000 pounds per inch of roll width; one of the said rollers being a hard, rough-surfaced roller heated to a temperature of from to 10 F. below thesoftening point of the synthetic polymer of the fabric and the other roller being an unheated compressible roller. In such a case, the pressure on the fabric is immediately released as the fabric emerges from the rollers.

The invention will be more readily understood by reference to the drawings.

FIGURE 1 is a diagrammatic flow sheet of the process of the present invention.

FIGURE 32 is a draftsmans conception of a photornicrograph of a fabric of the invention, having filaments 2 and 3 extending in the woof and warp directions. In FIG- URE 2, the extended protrusions are shown as small tapered protrusions 1 on the fabric surface. In many instances, however, the extended protrusions are shorter and appear much more like the smaller extended protrusions shown in FIGURE 2. In still other instances, the extended protrusions appear to be more in the form of scales projected outwardly from the surface rather than hair-like as shown in the figure.

FIGURE 3 is a draftsmans conception of a non-Woven fabric of the invention showing staple fibers 5 and extended protrusions 4 on the fabric surface.

The following examples are cited to illustrate the invention and are not intended to limit it in any manner.

Example I A taffeta fabric of loom count 104 ends x 76 picks is woven from 70 denier, 34 filaments of semidull poly(ethylene terephthalate) continuous filament yarn. Water at -200" F. is padded on the 42 inch wide fabric. Approximately 12 inches from the padding roll the fabric continuously passes over two stationary steel rolls and then moves another 12 inches to the top of the two calender rolls, each 48 inches in width. One roll is a steel Schreiner calender having v260 lines per inch and the compressible roll has a composition surface made of a mixture of cotton and corn husks. Excess water (which. is heated near the boiling point) wrings from the fabric at the nip. Excellent results are obtained with the sur-' 3 face temperature at the nip of the heated Schreiner roll at 440-460 F. The roll pressure is 1666 pounds per inch of roll width (i.e., 40 tons) and the roll speed yards per minute. Immediately after emerging from the nip of the rolls the fabric is quite stiff and boardy. It is then subjected to vigorous mechanical action while scouring at 190210 F heat set under slight extension in both warp and filling directions at 400 F. for seconds, and then subjected to the action of a 3% aqueous solution of sodium hydroxide at 212 F. until it loses 12% by weight. The fabric is then rinsed and dried. The fabric has a desirable subdued luster, a greatly improved covering power, and much softer and less slick surface, compared with the original untreated fabric. Microscopic examination of individual filaments taken from the fabric surface show that a profound change in surface characteristics has occurred. Each filament has numerous extended protrusions of a scaly nature.

Example 11 Two plain-weave blended fabrics are prepared, one 0 made from a blend of 45% cotton and 55% 3-denier poly(ethylene terephthalate) staple fiber having a staple length of 2.5 inches and the other being made from 85% poly(ethylene terephthalate) staple fiber and 15% rayon staple fiber, both having a denier of 3 and a staple length of 3 inches. Each of the two fabrics are processed under exactly the same conditions as those described in Example I except that a different heated roll is used and the treatment with sodium hydroxide is omitted. The heated roll is constructed as follows: a steel roll is sand-blasted, spraycoated with stainless steel and then spray-coated with aluminum oxide to give a surface having a randomly rough pattern. Substantially the same results are obtained as those set forth in Example I.

Example III A satin fabric is woven from 70 denier, 34 filaments of bright poly(hexamethylene adipamide) continuous filament yarn using a 1 x 4 twill weave, and loom count of 110 ends 2; 81 picks. This fabric is processed under exactly the same conditions as those described in Example II, except that the surface temperature of the heated roll is dropped to 400-410 F. The fabric is characterized by a pleasant subdued luster, a greatly increased covering or hiding power, good drapability, and a soft, almost suedelike, surface hand. Microscopic examination of individual filaments dissected from the fabric surface shows them to have numerous extended protrusions of a hairy nature.

Example IV A tricot fabric is knitted by feeding dull continuous filament poly(hexamethylene adipamide) yarns denier, 13 filaments with /2 Z twist) to both bars of the knitting machine, using 85 wales x 90 courses constructions. This fabric is processed under exactly the same conditions as those described in Example II, except that the heated roll temperature is 400-410 F. and prior to heat setting the fabric is subjected to rather severe temporary widthwise stretching to break up temporary bind points between and within the yarns. These tend to make the fabric excessively stiff and harsh unless the temporary stretching operation is applied. The extended protrusions (in the form of fine hairs) on the surface of this fabric increase the friction considerably, so that it is better suited to use as bed sheeting than an uncalendered control fabric. The improvement in friction is demonstrated by positioning fabric samples on an inclined plane surface at a angle and then placing a disc covered with woolen blanket material on the fabric-covered inclined plane. When the fabric covering the inclined plane is the unmodified tricot control sample, the disc immediately slides down the inclined plane. However, when the fabric covering the inclined plane is the tricot sample processed according to this invention, the blanket-covered disc does not slide down the inclined plane even when the angle is increased to 60. In addition to improved frictional properties, the tricot fabric wet calendered in accordance with this example has greatly improved covering and hiding power. Thus, while the light transmission of an untreated control fabric is 18.6% under standard test conditions, that of the wet calendered fabric of this example is only 5.2%.

Example V A knitted tissue tricot lingerie fabric is prepared by feeding dull continuous filament poly(hexamethylene adipamide) yarns (20 denier, 7 filaments, /2 Z twist) to both bars of a 32-gauge Reading Tricot Knitting Machine. The construction of the knitted fabric after finishing is 62 wales x 66 courses and the fabric weight is 1.9 oz./sq. yd. and the thickness is 0.006 inch. After knitting, the greige fabric is scoured in a Beck in water containing a commercial wetting agent at F. for one hour, then the fabric is dyed a green color in the Beck at the boil. The dyed fabric is dried on a pin tenter relaxed at wet width with overfeed at 250 F. for 10 seconds. The fabric is then subjected to a calendering treatment using two calender rolls. One is a Schreiner roll which is an engraved steel roll having 260 lines per inch running obliquely to the axis of the roll. The second roll is a compressible roll with a smooth composition surface. The fabric is dry calendered between the two rolls at 400 F. at a rate of 15 yards per minute, using 40 tons pressure which is slightly less than 1 ton of pressure on the fabric per inch of calender width. The fabric is then relaxed or heat set in a pin tenter at calender width with overfeed at 400 F. for 12 seconds. After this, the fabric is worked in a Beck in an aqueous bath containing a commercial cationic softening agent for the fabric at 180 F. for /2 hour. The fabric is then dried and the finished construction measured and reported as indicated above.

At this stage the fabric is divided into two parts and the second sample given an additional treatment in accordance with this invention. After Schreiner calendering and instead of heat setting, the second fabric sample is padded with water at 180200 F. Approximately 12 inches from the padding roll, the fabric continuously passes over a stationary steel roll and then moves another 12 inches to the nip of two calender rolls. The heated roll is a steel roll prepared by blasting the surface with sharp tungsten carbide particles, spray coating the surface with stainless steel, and then spray coating with aluminum oxide giving a surface having a randomly rough pebbled pattern. The second roll is a compressible roll having a composition surface made of a mixture of cotton and corn husks. Excess water which is heated near the boiling point is wrung out from the fabric at the nip of the two calender rolls. The surface temperature of the heated steel roll at the nip is 400 F. The roll pressure is 833 lbs/inch of roll width (i.e. 20 tons) and the roll speed is 14 y.p.m. The resulting calendered fabric is worked in a Beck containing water and a commercial softening agent for the fabric at F. for two hours, following which the fabric is removed from the Beck and dried.

The face of the two fabrics prepared in this example which is the side of the fabric away from the body is essentially the same in both cases. The back of each fabric, which is the side touching the body of the wearer, is different depending on the particular treatment as indicated above. The sample of fabric which has the additional hot Wet calendering applied had a surface which was rougher and less slick and therefore was much more comfortable in contact with the skin of the wearer than the sample which was processed without the hot Wet calendering step. The sample of fabric which had been subjected to the additional hot wet calendering treatment was examined under a microscope. This examination showed that the individual filaments on the surface of the fabric which was hot wet calendered contain a number of extended protrusions in the form of fine hairs which protrude outwardly from the surface filaments. It is believed that these hairs act to keep the surface of the fabric separated from the skin of the wearer allowing air to pass between the skin and the surface of the fabric and thereby reduce the ability of the fabric to or staple fiber from which it originates. With the somewhat circular hair-like protrusions, the average diameter of the protrusion is generally less than the diameter of the individual surface filament.

In this respect the structure of the surface of the fabric treated in accordance with this invention is distinctly different from the surface of fabrics made heretofore, such as those fabrics which have been napped, sueded, brushed, or crimped, as well as different from the more recently developed fabrics from textured and bulked yarns. In all of the cases prior to this invention the filamentous surface extensions are of essential-1y the same diameter and cross section as that of the original fiber or filament before napping, texturing or other treatment.

The present process is based on a critical selection of processing variables which must be controlled simultaneously in order to achieve the improved fabrics which are the object of this invention.

The temperature of the heated rough-surfaced roll at the nip should be maintained at 100 to F. below the softening point of the filamentary material used in the particular fabric being processed. This temperature will vary, depending upon the softening point of the fibers and filaments. For example, for polyamide fabrics the preferred hot roll temperature at the nip is 360 F. to 410 F., depending upon the fabric thickness. For fabrics constructed of acrylic polymer and copolymer filaments, the preferred hot roll temperature is 275 F. to 325 F. For fabrics constructed of polyester yarns, the preferred hot roll temperature is 425 F. to 475 F. The roll pressure at the nip should be such that enough hot water is retained in the nip to keep the fabric just wet-out during its passagethrough the nip. A satisfactory operating range of pressure is 500 to 2000 pounds per inch of roll width.

The speed of the two calender rolls carrying the fabric must be sufficiently high that the water enters the nip with the fabric before it can be heated to boiling temperature and flashed off. On the other hand, the speed must be sufficiently low to permit water in the nip to reach the necessary roll temperature depending upon the fabric type used. A satisfactory operating range of peripheral roll speed is to 35 yards per minute for most fabrics.

One of the most critical variables in the present process is the hot water which is employed in the nip of the rolls. Normally the fabric will be padded in water at a temperature of 175 to 225 F. at a point as close to the nip as practical. Excess water is then wrung out at the nip and drained back to the padding pan but allowing enough water to remain to keep the fabric wet-out. Normally the temperature of the wet fabric must be raised and maintained close to the boiling point of Water just before entry into the nip in order to avoid cooling the roll excessively, and yet the fabric must not be too hot or the water will flash from the fabric prematurely.

One of the calender rolls is normally made with a rough hard incompressible surface which allows the fabric to be compressed slightly below the surface of the roll in a number of points across the surface. The surface may be made of alloy steel, plastic, ceramic or coated metal such as chromium or nickel plated steel, and the surface is preferably rust-resistant. The second roll is made of a compressible composition, such as cotton, paper, wool, corn husk or other material that will present a tough resilient unpatterned surface to the fabric when compressed against the first roll. The action of the second roll is to seal the water within the nip and prevent expansion into steam before the water has been heated to or near the temperature of the hot roll.

The process of this invention may be modified by operating the calendering step at such a high speed that all of the water does not have a chance to vaporize, which results in the fabric issuing from the calender rolls in a state which is still damp. This results in a few extended protrusions on the surface of the fabric but the temperature at which the surface of the fabric is subjected in the hot wet calendering steps falls short of that required for heat setting the fabric. As a result, the fabric has a less stiff hand which is useful in some applications for making shifting, suiting, and the like withsofter and less boardy aesthetics.

While the scope of this invention is not to be limited by any particular theory, it is believed the critical conditions specified for calendering the fabrics cause numerous fine extended protrusions to be forced or drawn out of the individual filaments and fibers of a yarn without changing their external appearance. These protrusions are usually a fraction of the diameter of the filament itself and several times longer than the filament diameter. Their formation might be explained by the theory that moisture within the filament is heated under high pressure to a point approaching the flash temperature at that pressure. When the pressure is released, the moisture flashes into steam and pulls some of the polymer from the inside of the filament as it escapes. Through the microscope, it can be seen that any protrusions which are unobstructured shoot straight out of the filament, but those that exit within the yarn bunch up and force the filaments apart. This action upsets the symmetry of the yarn and results in increased fuzz or nap on the fabric, causing increased cover and decreased sheen. The volume of the filaments, yarns and fabric is increased; hence the fabric thickness is not decreased as is the case in conventional calendering of fabrics which flattens the yarn bundles. The critical processing conditions of this invention force hot water into the fabric structure and hold this water within the fabric in the liquid state under pressure until the water at the nip reaches the temperature of the surface of the heated roll. Then the pressure at the nip is instantaneously released, allowing superheated water to flash into steam and, by this action, to disrupt the smooth surface of individual filaments and fibers which have absorbed water. This essential action of disrupting the surface of the filamentary material is carefully timed and controlled to take place substantially entirely and immediately after the release of constraint rather than during the period of constraint.

The chief advantage of the present invention is that it provides a process for producing fabrics containing a preponderant amount of man-made filamentary material sim ilar in properties to fabrics constructed of conventional man-made spun yarns, with the added advantage that the fabrics of this invention contain many more minute extended protrusions or hairs, and each hair is much finer and softer than the conventional loose ends found in spun yarns. Hence, the calendered filament fabrics resulting from the present invention possess much improved friction qualities, especially p-olyamide tricot knit fabrics, than do conventional man-made spun fabrics. A further advantage is that the present invention provides a process for reducing and even removing sheen from fabrics constructed of man-made filaments and spun yarns, including blends of man-made yarns with cellulosic and/or natural yarns, increasing the cover of said fabrics, and reducing the slickness of said fabrics. Another advantage is the fact that the instant process produces fabrics from man-made filamentary material having much more comfort than those available heretofore because of the fine extended protrusions existing on the surface of the fabric in contact with the body of the wearer which tend to lift the fabric away from the body and prevent total contact between surface and body.

The process of the present invent-ion may be applied to any woven, knitted, or nonwoven fabric constructed from a preponderant amount of man-made filaments. The term filaments as used herein refers to either staple fibers or continuous filaments employed in making the fabrics. Typical examples of such man-made filaments include those prepared from polyamides such as poly- (hexamethylene adipamide), poly(hexamethylene sebacamide), polycaproamide, and copolyamides, polyesters and copolyesters such as condensation products of ethylene glycol with terephthalic acid, ethylene glycol with a 90/10 mixture of terephthalic/isophthalic acids, ethylene glycol with a 98/2 mixture of terephthalic/S-(sodium sulfo)-isophthalic acids, and trans-p-hexahydro-xylylene glycol with terephthalic acid, poly'acrylonitrile, copolymers of acrylonitrile with other monomers such as methyl acrylate or vinyl pyridine, vinyl and vinylidene polymers and copolymers, polycarbonates, polyurethanes, polyesteramides, polyethylenes, polypropylenes, fiuor-inated ethylene polymers and copolymers, and the like.

It has been found that the application of the hot-wet calendering treatment of this invention to the woven-like knitted fabrics made from spun yarns composed of 100% filamentary material or composed of blends of at least 50% man-made filamentary material with rayon or cotton, prepared in accordance with the method described by Chandler United States Serial No. 812,215, filed May 11, 1959, produces :a silk-like luster and improves the body, cover, and comfort of the fabric and these improvements are retained even after repeated launderings.

Considerable improvement in hand and cover also may be obtained when blends of man-made filaments with up to 50% by weight of cellulosic and/or natural filaments, such as cellulose acetate, cellulose triaeetate, viscose rayon, cotton, wool and the like, are processed in accordance with this invention. A shirt, blouse, dress, or similar garment can be made which will have an acceptable appearance and can be worn without ironing after receiving a complete automatic machine-wash, tumble-dry home laundry cycle. For best results, the garments should be tumbled-dried at 158:428 F. The garment can be made of a fabric containing an intimate blend in both warp and filling of at least 55% poly(ethylene terephthalate) filaments with viscose rayon as the remainder of the blend. Typical fabric constructions which will give the required performance are batistes, broadcloths, and oxfords. To have acceptable seam appearance after the machine wash and tumble-dry cycle, low thread tensions during sewing are required. As an example, tension in the range of 150 to 200 grams should be used on a lock stitch machine. In addition, it may be necessary to utilize special threads or special seaming devices to obtain the best seam appearance. As an example, a bobbin thread which elongates 5 to 15% on heating to 320 F. can be used to give the required seam appearance after the automatic avash-tumble-dry cycle.

Specific fabric types which are greatly improved with regard to aesthetics and comfort include tricot fabrics, woven undergarments, bed sheeting, pillow cases, shirtings, blouse and dress fabrics, and other apparel and industrial fabrics.

Many other equivalent modifications will be apparent to those skilled in the art from a reading of the foregoing without a departure from the inventive concept.

This application is a continuation-in-part of United States Patent Application Serial No. 746,341, filed July 3, 1958, now abandoned.

What is claimed is:

1. A fabric containing at least 50% by weight of filaments composed of a man-made non-cellulosic fiberforming polymer having a melting point above about 250 F. at least some of said filaments are located at the fabric surface and bear a multiplicity of extended protrusions which project outwardly from the fabric surface, most of the said extended protrusions of each individual filament extending outwardly from the side of the filament for a distance greater than the width of the filament and said protrusions being smaller in cross section than the filament at the mid-point of the length of the protrusion.

2. The product of claim 1 wherein the fabric is composed of continuous filament yarns.

3. The product of claim 1 wherein the fabric is composed of spun yarns.

4. The product of claim 1 wherein the fabric is knitted.

5. The product of claim 1 wherein the fabric is woven.

6. The product of claim 1 wherein the fabric contains both synthetic and natural staple fibers.

7. The product of claim 1 wherein the polymer is poly(hexamethylene adiparnide).

8. The product of claim 1 wherein the polymer is poly(ethylene terephthal-ate).

9. The product of claim 1 wherein the fabric is nonwoven.

10. The product of claim 1 wherein the polymer is a linear polyamide.

11. The product of claim 1 wherein the polymer is a linear polyester.

References Cited in the file of this patent UNITED STATES PATENTS 2,110,371 Radford Mar. 8, 1938 2,200,946 Bloch May 14, 1940 2,268,160 Miles Dec. 30, 1941 2,354,435 Stedman July 25, 1944 2,361,371 Hanson Oct. 31, 1944 2,420,565 Rugeley et al May 13, 1947 2,453,186 Binda NOV. 9, 1948 2,810,646 Wooding et a1 Oct. 22, 1957 2,834,093 Woodell May 13, 1958 2,853,741 Costa et a1 Sept. 30, 1958 3,015,873 Dietzsch et al. Jan. 9, 1962 

1. A FABRIC CONTAINING AT LEAST 50% BY WEIGHT OF FILAMENTS COMPOSED OF A MAN-MADE NON-CELLULOSIC FIBERFORMING POLYMER HAVING A MELTING POINT ABOVE ABOUT 250* F. AT LEAST SOME OF SAID FILAMENTS ARE LOCATED AT THE FABRIC SURFACE AND BEAR A MULTIPLICITY OF EXTENDED PROTRUSIONS WHICH PROJECT OUTWARDLY FROM THE FABRIC SURFACE, MOST OF THE SAID EXTENDED PROTRUSIONS OF EACH INDIVIDUAL FILA- 